Information architecture helps avoid waste and capture maximum value earlier in the development and test process. Agile and lean teams should always begin projects with information architecture for any project that will run eight weeks or longer.
Ultimately, not every project needs information architecture. Or design. How well you understand the problem and the solution, as well as how that understanding changes, determines whether or not you need architecture, design, development, or testing.
Information architecture defines what experiences are possible while design facilitates specific experiences. Understanding this distinction helps identify when you should or shouldn't persuade your project team that they need information architecture.